Curtis, 23, will wear No. 62 as he makes his Major League debut, in his third professional season. In 8 games for the Rawhide this season, he was 1-0 with 2 saves, 5.23 ERA (8 R-6ER in 10.1 IP), 12 hits, 5 walks and 22 strikeouts. He held opponents scoreless in 5 games, including 2 games with 2.0 scoreless innings and 5 strikeouts and 1 game with 2.0 scoreless innings and 4 strikeouts. He held lefties to a .214 average (3-for-14) with 10 strikeouts.

In 3 Minor League seasons, the 5-foot-9, 192-pounder is 7-5 with 49 saves, a 2.17 ERA (22 R-17 ER in 91.1 IP), a .193 opponents average (63-for-327), 29 walks and 139 strikeouts. He has a 13.7 strikeouts per 9.0 innings ratio (139 K in 91.1 IP, 364 BF).

Last season at Single-A Kane County, he was named a Midwest League midseason All-Star and in 53 games, had 33 saves, a 1.33 ERA (9 R-8 ER in 54.0 IP), a .176 opponents average (33-for-188), 12 walks and 75 strikeouts. He was the D-backs sixth-round pick in the 2014 Draft out of Middle Tennessee State University.

Hessler, 27, appeared in 2 games for the D-backs this season and 7 games for Double-A Mobile.